In TV, there are some “cold opens” that signal a shift in a show’s direction or tone or character. We saw that last week with the first minute of The Walking Dead’s season 4 premiere. We met farmer Rick and saw his ambivalence when he found a pistol buried in the ground. This opening scene presaged a major shift in two ways: (1) that post-Governor life in the prison had become so tranquil that lawman Rick could contemplate a semblance of order to his makeshift farm, and (2) that years of leading people fighting for survival had taken such a toll on a once-fearless warrior that he had gone the extra step to renounce weapons in hopes he could give his son a more normal existence.

The cold open from this season’s second episode, “Infected,” falls into another category: the mystery set-up, a scene that show us just enough to know thing are going to be really bad. The tight shot of a live rat illuminated only by flashlight, being fed through the fence to a waiting walker tells us we have a saboteur. Who is this person? And for what reasons could he or she even have for these actions?

“Infected” doesn’t answer those questions. The enemy-within plot is one that will play out over more episodes. But we did see the disastrous effects of those actions when a zombie horde nearly breached the outer wall of the prison. In a smart, and devastating, moment of cunning, Rick managed to lure the horde away by sacrificing the livestock he’s worked to cultivate. But more on that in a minute, first we have to address the emergence of the “woggers.”

The second part of last night’s opener played out through the classic horror-movie technique that goes something like this: the bad things you see are really bad; the bad things you don’t see—but that you know are there—are terrifying. Steven Spielberg used camera shots over and through dark water to create some of the scariest scenes in Jaws. The times we didn’t see the shark were far more frightening than the scenes where we did. As we followed Karen through the shower room, we knew that the zombie Patrick was in there somewhere. The tension mounted as she heard something and pulled aside a shower curtain to find nothing there (okay, that was kind of cliché, but it still worked pretty well).

But there was something there, and zombie Patrick almost chose Karen’s room before moving on to attack someone else, a nameless newcomer who was sacrificed to the zombie gods (because he happened to snore.) There seemed to be something different about zombie Patrick—how quickly he moved, how he attacked his first victim by biting him in the throat so he couldn’t scream—that suggests he’s no ordinary walker. For now, until we can come up with a more scientific name (please suggest some below), I’m calling this new breed of zombies the woggers: they’re faster than walkers, but they don’t quite jog; they move at a walk-jog—a “wog.” We saw from Patrick’s first victim that they look a little different, with more brightly colored eyes. After he rose from his bunk (with his guts spilling out all over the floor—a nice gory touch) he was the first zombie other than Patrick to attack people, not just to devour them as victims, but to leave enough intact so they join the wogger ranks in decent fighting shape.

When our group first faced the woggers in cellblock D, all hell broke loose. Woggers were intermingled with civilians; some were bitten and some were fine. They managed to get the security situation under control before turning to the question of how it all happened. Hershel (with a new cast member who seems to be a doctor), correctly traced the epidemic back to Patrick and realized he died of some kind of infection. Where did it come from? How did it spread? Does it create a new, more lethal version of zombie? To quote my favorite movie, The Big Lebowski, “Well, Dude, we just don’t know.”

And we probably won’t find out for some time. The infection narrative looks like it’s going to be a long play, and we didn’t get many clues from the closing scene. Poor Tyrese, just trying to bring his girlfriend flowers finds carnage and a blood trail through the bowels of the prison. He finds Karen’s charred body in a back courtyard, identifying her by her bracelet. Did she turn into a zombie just by being exposed to the disease? Who made the call to have her body burned? We’ll need to wait another long week to find out.

Gene Page/AMC

And now for a hail of bullets:

Zombie Kill Report:Dozens upon dozens, again boosted by the exterminations along the fence line. The fight in cell block D was sufficiently bloody with a smashing head stomp and plenty of walkers dispatched by Daryl’s crossbow. We even see Rick get back in the action with a very small pocket knife.

The Return of the King: Speaking of Rick, our fearless leader is back. But it wasn’t a pleasant journey. When the zombie horde nearly overruns a section of the fence, he quickly realizes they can’t kill their way out of the situation. The scene in which he sacrifices his pigs is powerful, not because we care about pigs, but because of the intense emotions that play across Andrew Lincoln’s face. Particularly devastating is his expression when he slices open the runt of the litter—we see the death of Rick’s dream of a tranquil life. In the end, he puts back on the gun, ready to roll into battle once more.

Michonne’s Tender Side: Before the season started, we said we wanted to see more character development out of Michonne. We got, through a few jokes, a little bit of that last week—in episode 2, we see a whole new side of the show’s greatest warrior. When Beth hands baby Judith to Michonne to hold for a second, Michonne breaks down. Earlier, Beth had asked why there was a name for someone who loses a husband (widow) or a child who loses his parents (orphan), but no name for someone who loses a child. We didn’t need to be told that Michonne once had a child that she lost. The scene—and a great performance by Danai Gurira—says it all.

And Carol’s Dark Side: I don’t know whether I’m impressed or worried about Carol, but I am surprised. Teaching kids to use knives in self-defense is one thing; encouraging a little girl to stab her father in the head before he turns into a zombie is quite another. Have the years of survival and struggle forced Carol to abandon her humanity to this degree? It seems a bit sudden, and she backtracks somewhat at episode’s end when she put a flower behind Lizzie’s ear. Maybe that’s the last we’ve seen of stone cold Carol—and, if so, then good riddance. Carol has more than proven her toughness and strength over the years, and she doesn’t need to act like a hardass who’s completely devoid of all feelings. There’s enough nastiness in The Walking Dead universe; let Carol be one of the good ones.

What did you think of last night’s episode? Are the new zombies really Woggers, or was I accidentally watching the episode at a higher speed? Weigh in below.